Problem: Simplify the expression. $(-5z-4)(-4z-7)$
Answer: First distribute the ${-5z-4}$ onto the ${-4z}$ and ${-7}$ $ = {-4z}({-5z-4}) + {-7}({-5z-4})$ Then distribute the ${-4z}.$ $ = ({-4z} \times {-5z}) + ({-4z} \times {-4}) + {-7}({-5z-4})$ $ = 20z^{2} + 16z + {-7}({-5z-4})$ Then distribute the ${-7}$ $ = 20z^{2} + 16z + ({-7} \times {-5z}) + ({-7} \times {-4})$ $ = 20z^{2} + 16z + 35z + 28$ Finally, combine the $x$ terms. $ = 20z^{2} + 51z + 28$